Fuel and torque control apparatus for aircraft propulsion systems



May 18, 1954 L. LEE u 2,678,698

FUEL AND TORQUE CONTROL APPARATUS FOR AIRCRAFT PROPULSION SYSTEMS Filed Nov. 15, 1946 2 Sheets-Sheet l FUEL PE, 1 SUPPLY IN VEN TOR.

9 AGENT ZEEIHTUN ZEEH L LEE u 2,678,698

FUEL AND TORQUE CONTROL APPARATUS FOR AIRCRAFT PROPULSION SYSTEMS May 18, 1954 Filed Nov. 15, 1946 2 Sheets-Sheet 2 INTERNAL COMBUSTION ENGINE (SEE FIG. 1)

TO "0 56 SOURCE OF FUEL PUMP 3282 4| P19. Z (P5) INVENTOR.

PROP.

PITCH CONTROL AGENT BHTUN ZEB U Patented May 18, 1954 FUEL AND TORQUE CONTROL APPARATUS FOR AIRCRAFT PROPULSION SYSTEMS Leighton Lee II, Rocky Hill, Conn, assignor, by mesne assignments, to Niles-Bernent-Pond Company, West Hartford, Conn, a corporation of New Jersey Application November 15, 1946, Serial No. 710,023

24 Claims. (Cl. 170-13534) The present invention applies to fuel and torque control apparatus for internal combustion engines, inclusive of gas turbine engines and combination gas-turbine-and-jet engines.

The particular embodiment of my invention, as described in the appended specification, is intended for control of fuel delivered to an internal combustion engine suitable for propeller-propulsion or combined propeller-and-jet propulsion of aircraft; and for control of the propeller torque. In general, it may be assumed that the propeller used with such an engine absorbs substantially the total brake-horsepower of the engine and that the ratio of propeller torque to engine torque is constant. the particular embodiment of the invention herein described, but the invention is not so limited.

An internal combustion engine such as is referred to herein includes a compressor, one or more combustion chambers, a turbine, and a tailpipe, in the stated order of arrangement. Associated with the engine is a fuel pump for delivering fuel to the combustion chamber and, connected to the compressor shaft, there is a gear train driving a propeller shaft and a propeller at a speed less than engine speed.

Ideal fuel requirements of this type engine are determined by proper analysis of empirical data which show the desired relationship of engine speed, fuel flow, brake-horsepower, altitude, temperature, and other factors, to each other. A measured indication of mass air flow thru the engine may be employed as one means. of obtaining fuel flow control. The significance of the fuelair ratio, however, is less apparent than when dealing with reciprocating engines, owing to metallurgical and structural limitations which prevent safe operation at speeds and temperatures exceeding predetermined limiting values. Engine speed and temperature vary in response to a wide variety of conditions which include brake-horsepower and engine torque, and it is desirable to maintain the respective values of speed and temperature in definite relationship with limiting values thmout the range of operation. Therefore, the fuel flow may be made a continuous function of engine speed and temperature.

Because a fixed-pitch propeller cannot perform equally well under all conditions of flight, it is customary to employ variable pitch propellers. It is then possible to obtain relatively high propeller efficiency with a low-pitch setting under conditions of take-01f and climb at relatively high engine speed and power; andv to obtain correspondingly high efficiency with. a higher pitch set- This assumption applies to ting under normal conditions of cruising speeds and power. Variable pitch propellers are used to obtain constant engine speed, when desired,

For a given condition of engine speed and brakehorsepower, engine torque varies according to the relation:

k B. H. P.

R. P. M.

in which T, k, B. H. P., and R. P. M. are respectively the engine torque, a constant, the engine brake-horsepower, and the engine speed. Pro,- peller efficiency is defined as the ratio of thrusthorsepower to engine brake-horsepower and is a,

function of pitch and propeller characteristics, whence variable pitch control affords means whereby the relationship between engine speed, brake-horsepower, and torque, may be controlled in flight.

It is an object of the present invention to provide improved control apparatus for regulating both the fuel flow and the torque of an internal combustion engine.

Another object is to provide, in apparatus of the type described, improved means for regulating both the fuel flow and the torque as functions of an air pressure in the engine which is a measure of the mass air flow therethru.

Another object of this invention is to provide in such apparatus improved means, including a single manually operated lever, for controlling both fuel flow and torque to satisfy particular operational requirements of speed and torque.

It is a further object of my invention to provide improved fuel and torque control apparatus of simple design whereby the engine may be operated at constant maximum speed and varying load.

Other objects and advantages of the present,

invention will become apparent from aconsideration of the appended specification, claims, and drawings, in which:

Figure 1 illustrates, somewhat diagrammatically, fuel and torque control apparatus embodying the principles of my invention and the relationship of such apparatus, an internal combusticn engine and associated means which include a fuel pump and a pitch control mechanism; and Figure 2 illustrates, also somewhat diagrammatically, another embodiment of my invention and its principal connections with the engine and associated means of Figure 1.

FIGURE 1 Referring to. the drawing, Figure 1', there are shown the principal elements of an internal combustion engine suitable for propeller-propulsion or propeller-and-jet propulsion of aircraft, as follows: a supporting casing I0, an air inlet I2, a multi-stage compressor indicated as I4, a compressor rotor shaft !6, a combustion chamber I8, a number of fuel discharge nozzles one of which is designated 20, a generally circular manifold 22, a multi-stage turbine indicated as 24, a turbine rotor shaft 26 connected to the compressor rotor shaft it, a tailpipe 28 for discharge of combustion gases from turbine 24, a center bearing 30 and end bearings 32 and 39 supported by casing I0, a propeller shaft 36, and a gear train 38 connecting shaft 36 to shaft I6.

In the hub 46 of the propeller generally shown as 42, there is an hydraulically operated pitchcontrol diagrammatically shown as 44, for varying the pitch of the propeller blades 46. Pitch control 44 is connected by a conduit 48 to the control apparatus subsequently described, and by another conduit 49 to a convenient source of engine oil.

A tube 50 is connected to the engine and supplies air to the control apparatus at the static pressure in air entrance I2. Similarly, a tube 62 is connected to the engine and supplies air to the control apparatus at the static pressure downstream from compressor I4.

A compressor pressure differential is thus obtained which is a function of the compressor characteristics, the engine speed, air entrance pressure and temperature, and variable conditions downstream from the compressor, including variations in combustion temperature, in the fuel flow to the engine, and in the brake-horsepower. The differential is an indication of air flow thru the engine; assuming constant engine speed, the differential decreases as altitude increases or as entering air density decreases, and it also decreases as the combustion temperature increases.

fhe fuel manifold 22 in the engine is connected by a conduit 54 to a variable delivery fuel pump Pump 56 is driven by the engine thru gearing and is connected to a source of fuel by a fuel inlet conduit 69.

Referring to the control apparatus of Figure 1, there is shown an oil supply conduit 62 for the fiow of engine lubricating oil, at a pressure (111), to an inlet conduit 64 and thence to a pump 66 having a constant delivery at any given speed. Pump may be driven by the engine and has sufficient capacity to provide high pressure at low starting speeds. From the pump oil flows at superatmospheric pressure thru a conduit 66, whence the course of flow is briefly described as follows: a first path of flow from conduit 68 includes a conduit M, a by-pass valve mechanism '56, and a drain conduit 84 connected to supply conduit 62; elements 68, M, 76, 84, and 62 being connected in series in the order stated. A second path of flow from conduit 68 includes a re striction I6 and a chamber 96 in a pressure regulator I2. The flow from chamber 96 is divided thus: part of the oil entering chamber 96 flows therefrom thru a valve seat I02 in pressure regulator if, then thru a conduit I04 connected to seat its and thence to drain conduit 84; and the remainder of oil entering chamber 96 flows thru N a conduit I56, a control valve mechanism H8, a conduit I36, another conduit I38 having therein a fixed restriction I40, and drain conduit 84; elements 96, H6, H8, I36, I38, and 84 being connected in series in the order stated. Conduit 68 is also connected to a conduit 18 for flowing oil to elements of the fuel control hereinafter described.

The by-pass valve mechanism I6 comprises a body 90 having a chamber 82 therein. A valve seat 60 is in body at the lower end of chamber 62 and is connected to conduit I4. The upper end of chamber 82 is connected to conduit 84. A spring 06 is in compression between the upper end of chamber 32 and a valve 88 which is forced by spring 86 toward seat 90, thereby tending to restrict flow thru the seat with a substantially constant spring force. In consequence of the action of valve 88, the by-pass valve mechanism I6 maintains a substantially constant superatmospheric pressure (:02) in conduit 69, the value of which pressure depending on the rate and initial loading of spring 86.

The pressure regulator 72 includes a body 92 and a diaphragm assembly 94, which together form chamber 96. A diaphragm 95 in assembly 64 is held in position by a diaphragm retainer 98. A valve I00 is attached to the diaphragm assembly 94 and is operable in response to movement of assembly 94 to vary the effective area of flow thru valve seat I02. A spring I06, in compression between diaphragm assembly 94 and a retainer I08, tends to move valve I00 toward seat 02. The closing force on valve I60 due to the pressure differential thereacross is negligible. Valve I is therefore subject to opposite forces; namely, a spring force tending to close it, and an opening force produced by the pressure differential acting on diaphragm assembly 94.

Since the lower side of diaphragm 95 is vented to atmosphere, it follows that in a condition of equilibrium the gage pressure (103) in chamber 96 is proportional to the load imposed by spring I06 tending to seat valve I90. For every fixed position of spring support I08 there is a corresponding substantially constant spring load and hence a corresponding substantially constant value of the pressure (103). The control apparatus is not limited to use of atmospheric pressure for balancing diaphragm 95, as other preferably low pressures are suitable and may be used, if desired.

The particular value of pressure (pa) in chamber 96 is controlled by the position of support I98 which is operable by a cam IIO to vary the deiiection of spring I06. Cam H0 is mounted on a shaft H2 which is rotatable thru an arc of predetermined length by a manually controlled lever H4.

Both the volume and the pressure of oil flowing from the by-pass valve mechanism I6 are subject to wider variations than the corresponding volume and pressure of oil flowing from the pressure regulator I2. Regulator i2 is therefore of relatively smaller capacity and greater regulating accuracy than the mechanism 76. A single valve could perform the functions of both valve mechanisms l2 and IE; but, if located at the pump, a long and complicated valve control mechanism would be required; and, if such a single valve was located at the control apparatus, long and high-oapacity lines to the pump would be necessary. The arrangement shown in Figure 1 is well adapted to an installation in which the fluid pump is remotely located in respect to the rest of the control apparatus.

Control valve mechanism IIB includes a housing I26 having therein an upper chamber I22 and a lower chamber I24. A bellows i26 is fixed to body I 20 in the upper end of chamber I22 and is connected to a valve I28 which operates in a guide I33 in body I20 at the lower end of chamber I22. The end of valve I28 is contoured and is operable in response to contraction of bellows I26 in opposition to a spring I3! to increase the effective area of a valve seat I32 at the upper end of chamber iz i. An inlet chamber I34 is formed in body between the lower end of guide I39 and the upper side of seat I32. Chamber I34 is connected to conduit IIS and chamber I2! is connected to conduit lit. The pressure (50;) in conduits I36 and I 38 is regulated as a function of the value of pressure (:03) the contour of valve I28, and the position of valve I28 relative to its seat I32. The pressure (124) increases as the pressure (323) increases or as the area of now past valve I28 increases and hence as bellows I26 collapses.

The chamber I22 is connected by a conduit I42 to another conduit I51 and thru a restriction its to the compressor discharge pressure tube 52. The exterior of bellows I25 is thereby always subject to the pressure designated (10 in conduit Hi2 and chamber I22. The interior of bellows I26 is connected by a conduit Hit to entrance pressure tube 50 thru an outlet chamber I48 in a thermal control generally indicated as Its, and is always subject to the pressure (p Thermal control I59 comprises a body I52 having' a wall 65s separating outlet chamber I 18 from an inlet chamber I55 which is connected to conduit 55E. One end of a thin walled tube I53 is fixed to the closed end of body I52 nearest chamber I lri; and has attached to its other end, which is closed, a rod Hill which is slidable in a centrally located aperture I62 in the end of body I52 to which tube E58 i fixed. The free end of rod It?) is contoured to form a valve I6 5, which is operable in a seat in wall I54. Tube I58 and rod ltd are made from materials having substantially different coefficients of thermal expansion and the unit is installed in the engine with tube I58 exposed to the temperature of combustion gases in the tailpipe, as shown diagrammatically, or in some other desired location. As the temperature increases, the tube IE8 expands faster than the rod I69, thereby increasing the eifective area of opening between valve I64 and seat I68. Generally, control I56 is made so that the valve remains closed until a limiting value of temperature is exceeded.

When valve its is closed, as is normally true, the pressure in chamber I22 outside bellows I26 is the same as the pressure in conduits I42 and 5? and tube '52, there being no flow thru restriction its; hence the pressure (p pzthe pressure (11 when valve Hill is closed. Since the pressure inside bellows IE5 is always the pressure (p tube 59, then in normal operation below the limiting temperature bellows I25 is subject to the ressure dififerential (PD-27E).

When valve is open, however, as is the case when the value of limiting temperature is exceeded, iiow occurs thru tube 52, restriction IM and conduit iEl, past valve Hi l and into tube 55). The pressure in conduit I5! and hence the pres sure in conduit M2 is then less than that in tube 52, because of the pressure drop across restriction I ia, the pressure decrease being a function of the respective areas of restriction Md and of the opening past valve 564. When the valve is open, therefore, the pressure is less than the pressure (p and the bellows is subject to the pressure diiferential (p -p which, in this case, is less than the differential (p -41 in which (S) is the load on spring ISI corresponding to a reference position of valve I28 at which the travel t) is considered equal to zero, (s) is the rate of spring I3I, (A) equals the effective area of bellows I26, and in which downward movement of the valve is designated by a positive value of (t). Thus, for each value of the pressure differential (p -p there is a corresponding position of the valve and hence a corresponding value of the effective area of valve opening, depending upon the contour of valve I28. For a given contour, when the temperature does not exceed the predetermined limiting value at which thermal control valve I64 opens, it follows that the pressure (104) in conduit I36 varies as a function of the pressure (193) and the pressure differential p -p Conduit I35 has its lower end connected to the interior of a bellows I58 which has its upper end fixed to the upper end of a chamber Ill} in a body In of a pitch control pressure regulator indicated as I'M. In the lower end of body I-IZ there is another chamber I15 having a bellows I18 fixed to its lower end, bellows its and I78 oeing symmetrically disposed to each other in body I12 and being connected by a valve I80 which is operable in a guide I82 provided in a centrally located constriction I84 in body I12. Bellows I68 and I18 are identical in the embodiment of Figure l but may be of different sizes, if necessary, to satisfy particular requirements of design or operation. Both chambers IIII and H6 are vented to the atmosphere as shown, or to any other suitable common pressure source, thru vents I86 and I88, respectively. Valve i80 has a neutral position at which it remains in equilibrium when the pressure (734) in bellows I63 is equal in value to the pressure in bellows I18, assuming bellows I68 and Ill; to be of equal effective area.

The pressure (pi) is applied to bellows I68 as a measure of desired torque while the pressure (be) acting on bellows H8 is a corresponding. measure of actual torque derived as follows:

There is shown a torque meter I93, including: a sun gear I92 fixed to a forward section of propeller shaft 36, a torque ring I94 concentric with gear I92 and connected thereto by three symmetrically disposed planet gears IQS rotatable on stub shafts I98 fixed to torque ring I94. An outer ring gear Zilll engages the gears I93 and is fixed to a rearward section of shaft 36, the forward and rearward sections of shaft 36 being substantially the equivalent obtainable by cutting thru a single shaft at right angles to the shaft center-line. The force required to hold the torque ring I94 stationary is a measure of shaft torque and is transmitted. by means of a spring 209, thru a lever 202 attached to torque ring I94 to a piston 204 in a pressure control mechanism IlIlIi.v Mechanism 295 controls the pressure (105) inside bellows I'Ili by regulating the flow of oil from conduit is, thru a conduit 228' into pressure control mechanism 2%, past a valve 2I8 attached to the other end of piston 204, from mechanism 266 thru a conduit 22s and thence thru a restriction 226 to, drain conduit 84} elements 18, 220; 2Il6, 22 i, 226 and Bdbeing connected in series in the order stated.

A body 2% included in the pressure control mechanism 296 has a cylindrical bore 2I0 opening at one end of body 208 for admission of piston 284 which is slidable in the bore. The other end of body 208 is closed; and, between the closed end of body 208 and piston 264 there is a wall 2I2 which forms chambers 2M and 2I6, respectively, on the upstream and downstream sides of valve 2I8. Valve 2I8 varies the area of opening between itself and a valve seat 2i9 in wall 2E2, in response to movement of the piston. Chamber 2 I4 is connected to conduit 221i and chamber 2I6 is connected to the interior of bellows Us by a conduit 222, and also to conduit 224. In operation, the piston 29% is subject to the force of spring 239 and an opposite force resulting from the pressure (pa) in chamber 2I6 which tends to move valve 2I8 toward its seat. When the force due to spring 209 exceeds the force due to the pressure in chamber 2E6, the piston moves toward the right to increase the opening of valve 2I8 and hence to increase the pressure in chamber 2I6 until the force of spring 209 is balanced.

The position of piston 204 at different conditions of equilibrium variesslightly depending on the design of valve 2E8, and the corresponding variation in movement of lever 202 depends on the rate of spring 289. The pressure in chamber 2I6 and hence the pressure (125) in bellows I18 is thus maintained proportional to actual torque according to a substantially constant ratio of the pressure (105) to the torque measured by torque meter 98. The restriction 226 provides continuous flow past valve 2 I 8, thereby rendering it possible for the pressure in chamber 2I6 to decrease when the torque, and hence the force of spring 269, decreases and piston 204 moves to the left to close valve 2 I8.

Valve IBIi in pitch control pressure regulator I'M is thus subject to forces due to the pressures (p4) and (p5) respectively, which are correponding measures of desired and actual torque. Regulator I14 functions to make the value of (pa) equal the value of (504) so that a condition in which the actual torque is the desired torque may be realized.

A groove 228 is provided in valve I88 approximately opposite the center of length of guide I 82 in constriction ltd of body I72, when the valve is in its neutral or equilibrium position. The lower end of conduit 78 is connected to a port 239 in guide I82 below groove 228, port 23D being just closed by the valve when valve 80 is in its neutral position. Similarly, one end of a conduit 232, having its other end connected to drain conduit 84, is connected to a port 23 in guide I82 above groove 228, port 2% also being just closed by the valve when valve I 83 is in its neutral position. Conduit =28 has its lower end connected to constriction I84 of body I12, at the approximate center of the groove 228, when valve I8!) is in neutral position; and serves to connect the propeller pitch control 44 to the annular chamber between guide I82 and the grooved portion of valve I80. The pressure (126), hereinafter referred to as the pitch control pressure, is thus transmitted thru conduit 43 from the pitch control pressure regulator I'M to the propeller pitch control 44, which serves to increase the propeller pitch and hence the torque as the pressure (2.76) increases, assuming that the speed remains con stant.

When the value of 25) is less than that of (104) or when actual torque is less than desired torque, valve I8!) is moved downward, thereby permitting 8 the relatively high pressure of oil in conduit '18 to be transmitted past valve I86 thru conduit 48. increasing the pitch control pressure (pa) which in turn increases the actual torque. As the value of actual torque continues to increase, increase of pressure (106) is stopped when the valve I is restored to neutral position, or when the actual torque equals desired torque and (p5) =(p4). Should the value of be greater than that of (m), as when the actual torque exceeds desired torque, valve I88 is moved upward, thereby permitting a reversal of the above process by causing how from conduit 48, past valve I80, and thru conduit 232 to drain conduit 84, thereby decreasr ing the pitch control pressure (be) which in turn decreases the actual torque. As the value of the actual torque continues to decrease, the decrease of pressure (pc) is stopped when the valve I88 is restored to neutral position, or when the actual torque again equals the desired torque and (p5) (234) The amount of flow occurring past valve I80, from conduit 18 or to conduit 232 is to some extent dependent on the peculiarities of construction of the propeller pitch control mechanism and the amount of leak at valve I89 which may be made negligible or deliberately established at a value known to produce best performance.

The pitch control pressure conduit 48 is connected across valve I80 to a conduit 236 which enters a body 238 of a governor mechanism indicated as 240. As subsequently explained, the governor mechanism serves to modify the torque control pressure (pa) and/or the motor pressure (127) when the engine speed deviates from a predetermined desired value. The modified pressures produce increased torque and/or lower fuel flow when the engine speed exceeds the predetermined value; and, conversely, they produce decreased torque and/or increased fuel flow when the engine speed falls below the predetermined value.

Governor mechanism 246 comprises a speed responsive device indicated as 242 mounted in body 238 and driven by a gear 245 at a speed proportional to the engine speed. In body 238, there is a valve guide 243 and a valve 253 operable therein in response to device 242 which is connected to valve 250 at a groove 243 at the lower end of the valve. A spring 252 is in compression between a support 254 and the upper end of valve 259, which extends beyond the upper end of body 238. As the engine speed increases, the speed-responsive device 242 tends to move valve 258 upward relative to guide 248, in opposition to spring 252, and valve 250 is in equilibrium and stationary when the opposed forces due to spring 252 and to the speed responsive device 242 are equal. The position of spring support 254 is variable by means of a cam 255 which is operable on a shaft 25s in response to movement of a manually controlled lever 286. The particular value of engine speed, at which valve 256 is in its neutral or equilibrium position, is determined by the load on spring 252 and hence by the position of lever 286.

Valve 250 is provided with a pair of undercut portions of its length, 266 and 262, and guide 248 is provided with ports 264, 266, 268, 270 and 212 in body 238, the respective efiective areas of how thru ports 264, 268 and 212 being controlled by movement of valve 248. In its position of equilibrium, the valve just closes ports 264 and 268 and port 212 is slightly below the lower valving end of undercut 262 so that a slight speed decrease is required to open it. Ports 256 and 21s remain open thruout the range of operation of valve Port 25 5 is connected by a conduit 2M to main oil supply conduit 78. Port 2% is connected to conduit 23%; and port 2'32 is connected to a conduit 215 which in turn is connected to conduit 236. Port 210 is connect ed by means of a conduit 210 to drain conduit 8d and port is connected to an hydraulic motor 280 by means of a conduit 282. Shaft 256 is connected to an engine control shaft 280 on which is mounted the engine control lever 286 which is rotatable thru an arc approximating 90 relative to a fixed quadrant 283. A link 2% connects lever i M to a lever 258 fixed to shaft 256 so that movement of cams H0 and 255, and hence the respective loads on springs I06 and 252, are subject to simultaneous regulation by the control lever 206.

During a first predetermined ran e of lever movement, from zero position to approximately 20 degrees, in the embodiment shown, the lift of cam H0 remains at a constant minimum value. The pressure (:03) therefore has a constant minimum value, and the pressure (pi) measuring desired torque varies as a minimum-valued function of the air pressure differential (p Simultaneously, as the control lever is advanced thruout the first range, the lift of cam 255 increases so that the predetermined speed at which valve 250 is in neutral or equilibrium position increases from minimum value to an intermediate value which, in the embodiment shown, approximates 10,000 R. P. M. Thus in the first range of control lever movement, engine torque is of substantially coonstant minimum value and engine speed increases from minimum value to approximately 10,000 R. P. M. as the lever is advanced.

Durin a second predetermined range of movement of control lever 286, or approximately from twenty degrees to thirty degrees as indicated by quadrant 288, the lift of cam I I0 increases slightly, with consequent increase in the value of pressure (p3), and the pressure (174) measuring desired torque and hence the actual torque increase slightly thruout the range of values of a dinerential (p -p,,). Simultaneously, the the control lever is advanced thruout the second range, the lift of cam 2555 continues to increase so that the predetermined speed at which valve 250 is in neutral or equilibrium position increases from an intermediate value, or from approximately 10,000 R. P. M. in the control of Figure 1, to the maximum or limiting speed which approximates 13,900 E. P. M. in the particular engine of Figure 1. Thus, the second range of lever movement, as the control lever 286 is advanced, the torque increases slightly at all values of the differential (p ,-p,,) and the engine speed is increased to a limiting or maximum allowable value. As control lever 286 is further advanced thruout the third or final predetermined range of movement, approximately from 30 to 9 in the case shown, the lift of cam l 10 increases to a maximum value and hence the engine torque increases from value slightly greater than minimum to a maximum value. Simultaneously, the lift of cam 255 remains constant so that the predetermined engine speed remains a constant maximum value, regardless of torque changes.

The hydraulic motor 280 comprises a body 23! having a generally cylindrical bore 29| in which there is a piston 202, a rod 294, and a lever 296 10 for operating the delivery varying means associated with pump 56. Piston 292, rod 294, and lever 296 are so connected that upward movement of piston 292 causes clockwise movement of lever 20% and increases the pump delivery. The piston 292 is subject to a motor pressure differential between the motor pressure (p7) in a chamber 298 at the lower end of bore 253! which is connected to conduit 282, and the pressure (201) in a chamber tilt at the upper end of bore 29 I, chamber 3530 being connected to oil supply conduit 62.

A spring 3&2 biases the piston in opposition to the motor pressure (p1). Since the pressure (201) and the rate of spring 302 are substantially constant, it follows that the pump delivery varies as a function of the motor pressure (107), increasing as the control pressure increases.

The pitch control pressure regulator ll i is rendered subject to override by the governor mechanism 248 which simultaneously controls the motor pressure (P7) and hence the fuel flow to the engine. Assuming that valve Hit in regulator I'M is in its neutral position, and that valve 250 in overnor mechanism 2% is likewise in its neutral position, desired speed and torque values predetermined by the position of lever 288 will exist until the equilibrium of either or both valves is disturbed by one or more of several factors affecting engine operation. While a condition of desired speed and torque exist, it follows that the fuel flow is necessarily correctly controlled by proper regulation of the motor pressure (p7) which is a function of the governor valve mechanism 240.

In starting the engine, it is necessary to accelerate the rotor by external means to a critical relatively low value of speed at which auto-ignition and self-operation take place. This speed approximates-8,000 R. P. M. in some engines of the type shown and is referred to as the minimum operating speed, minimum engine speed, or minimum speed.

Operating condition (A) TORQUE CORRECT; ENGINE SPEED LOW Considering the first range of movement of control lever 286 in which only the engine speed is varied while the torque is desired to remain at substantially constant minimum value, it is assumed in a condition (A) that the lever is advanced to a position corresponding to a speed between 8,000 and 10,000 R. P. M., and that, while the torque is correct, the speed of the engine is below the desired value. In this condition, valve N30 is in its neutral position. Valve 250, however, is below its neutral position and therefore it provides a continuous oil passage from conduit 23% across mechanism M0 to conduit 232.

It is provided that the pitch control pressure (206) at the minimum value of torque is relatively greater than the value of pressure (p7) required at the motor 280, so that pressure (pc) is used as a source of relatively high pressure for regulation of pressure (107). Thus as the continuous passage above referred to is opened in condition (A), pressure (p7) increases, the fuel delivery increases, and the engine speed is increased.

Simultaneously, the pitch control pressure in conduit 48 decreases; and, in consequence, the propeller pitch decreases, the torque decreases owing to the change of pitch, the force supplied by torque meter Hit decreases and there follows adecrea-se in the value of pressure (pa) in bel lows H8. This series of reactions results in disturbance of regulator I14 from its condition of equilibrium, and valve I80 is caused to move downward, thereby permitting oil at the relatively high pressure (22:) in conduit is to flow thru port 235 into undercut 228 and then into conduit 48. The pitch control pressure (:06) is thus restored to its desired value, so that the actual engine torque remains substantially constant at the desired minimum value and the engine speed is increased to the desired value predetermined by the position of lever 286, the speed correction being due to increased fuel flow.

In the preceding paragraphs, the condition produced by flow of oil at pressure (126) to conduit 282, at pressure (pi), is treated independently of a number of concurrent reactions. For example, as the torque decreases owing to the temporary change of propeller pitch which follows temporary decrease of pressure (106), the

engine load decreases and hence the speed increases. This, however, manifests a temporary condition in which the torque and not the speed is below the desired value, the reverse of circumstances originaliy true in condition (A). This and corresponding concurrent reactions are of minor consequence, however, and the principal response of the apparatus to condition (A) is relatively unimpeded by such concurrent reactions.

In the event that, in condition (A), the engine speed falls so far below the desired value that valve 250 moves still farther downward to uncover port 272, oil may flow from conduit 23%, not only to conduit 282 as previously explained, but also thru conduit 21B and port 272, past undercut 262, and thru port 210 and conduit 2?8 to drain conduit 84. The pitch control pressure (226) in conduit 48 and hence the engine torque are thus correspondingly further reduced. In this case, the engine is temporarily deliberately unloaded by governor mechanism 240 in order to increase the engine speed.

With both port 212 and port 268 now uncovered, it is apparent that the motor pressure (177) in conduit 282 does not increase as rapidly as a result of flow from conduit 236 to conduit 282, as is the case when port 268 is open and port 212 is closed, as explained in earlier reference to condition (A). Therefore, as the engine is deliberately unloaded to increase its speed, there is a. temporary condition during which the motor pressure (in) and hence the fuel flow are slightly less than would be the case if valve 250 moved downward without uncovering port 212.

The engine speed increases with extreme rapidity,

however, when port 212 is uncovered, quickly approaching the predetermined desired value, and valve 250 is correspondingly quickly raised to a position at which port 212 is again closed. The relatively greater reduction of the pitch control pressure (pa) in conduit 48 which follows opening of port 212 and consequent decreased torque produce a still lower value of the pressure (305) in regulator 57 5 than was true in the case previously explained when the engine speed was not suihciently low to cause opening of port 212. Valve Hit in regulator H4 therefore more quickly responds to uncover port 230 and allows oil at the relatively high pressure (212) to flow from conduit 18, thru a greater effective area of opening thru port 230, past undercut 238 and into conduits 236 and 38, thereby restoring the desired values of pressures (in) and (p6), whereby both the fuel flow and the torque are restored to desired values.

Operating condition (B) TORQUE CORRECT; ENGINE SPEED HIGH Again considering the first range of movement of control lever 286 in which only the engine speed is varied while the torque remains at substantially constant minimum value, and assuming a condition (B) in which the engine tends to overspeed when the lever 285 is moved to a position corresponding to a speed between 8,000 and 10,000 R. P. M. As indicated by the calibrated quadrant 288, valve 250 is above the neutral position shown in Figure 1.

In this condition, a continuous oil passage is provided from conduit 282 to drain conduit 218 and the motor pressure in conduit 282 and chamber 2538 is consequently reduced. The fuel pump delivery is therefore reduced and the engine speed is hence decreased. Simultaneously, however, a second continuous oil passage is provided from conduit 27 to conduits 236 and 48, and the pitch control pressure (236) is increased and hence the torque increases and tends to decelerate the engine. The eifect on torque just described is a temporary one. While both a decrease in fuel flow and an increase in torque are shown to be simultaneously co-operative in arresting the over-speeding of condition (B), nevertheless when the predetermined speed is finally obtained, the torque is restored to minimum value and the fuel flow is reduced to correspond to the reduction of speed from the over-speeding of condition (B) to the desired condition at which the actual speed has a value agreeing with that indicated by position of control lever 286. The temporary increase 'in torque occurring during this process is minimized by action of the device lid which moves valve I36 upward to drain oil from conduit 48 to conduit 232 when the torque exceeds the desired value.

Operating conditions (C) -(J), incl.

Considering the third range of movement of control lever 22% in which the desired engine speed has a maximum or limiting value while the torque is varied from a value slightly greater than the minimum to a maximum value corresponding to the maximum brake-horsepower of the engine, at any point in this range in which the desired conditions apply the valves 250 and I are in their respective neutral or equilibrium conditions. One or more of several factors can disturb the condition of equilibrium of either valve, however, and both may be disturbed at the same time so that a range of conditions may result in which the torque is either as desired or higher or lower than desired; while the speed is respectively as desired or lower or higher than desired. The following conditions (C) to (J), inclusive, involve deviations from desired torque and speed settings.

Operating condition (0) TORQUE HIGH; ENGINE SPEED CORRECT In condition (C), the engine speed has a limiting value as desired and the engine torque is higher than desired, valve 250 therefore being in neutral position while valve is above its neutral position. A passage is thus provided for flow from conduit 48 to conduit 234 and thence to drain conduit 84, whereby the pitch control pressure (p6) and hence the torque is decreased. Such torque decrease produces an increased speed which is compensated by valve 250 which rises from its neutral position as the speed increases suming perfect operation of the apparatus, both torque and speed control changes occur simultaneously; the amount of change of either approaching an infinitesimal value when the desired condition of speed and torque is approached, provided the sensitivity of response of and to the control is satisfactory and that no new torque or speed develops during the process described.

Operating condition (D) TORQUE LOW; ENGINE SPEED CORRECT Condition (D) differs from condition (C) in that the torque is initially below rather than above the desired value, the engine speed being maximum as desired. In this case, valve 250 is initially in neutral position While valve 489 is below its neutral position and provides an oil passage from conduit 78 to conduit -38, thereby increasing the pitch control pressure (in) and the torque. The torque increase is attended with a speed reduction and consequent lowering of valve 25 to a position at which there is a passage for oil from conduit 236 to conduit 282 and a resulting fuel flow increase and hence a speed increase, as previously explained. The process of gradual torque increase and speed compensation continues until the torque is restored to the higher value desired and the speed is maintained at the desired limiting value.

Operating condition (E) TORQUE CORRECT; ENGINE SPEED HIGH In condition (E), the engine overspeeds but the torque is as desired. The speed is reduced b operation of valve 25s to reduce the motor pressure (pi) the valve moving upward to permit now from conduit 232, thru port 268, past underout 262, into port 248, and thru conduit 218 to drain conduit 8 Simultaneously, oil is permitted to flow from conduit 27d, thru port 254, past undercut 28 and thru conduit 23% to the pitch control pressure regulator I'M. The pitch control pressure (:00) is thereby increased, the torque increases and there is a corresponding speed decrease supplementing the speed decrease produced by the fuel flow decrease referred to. In response to the torque change, torque meter I96 and mechanism 295 co-operate to increase the value or pressure (295). This causes valve I86 in regulator iii! to rise, thereby allowing oil to flow thru port 22 and conduit 232 to drain conduit 84, the pitch control pressure (pa) being thereby restored to the desired value. Thus, in this process of correcting a condition of overspeeding the efiect on torque is temporary.

Operating condition (F) TORQUE HIGH; ENGINE SPEED HIGH In condition (F), the engine overspeeds and the torque is higher than desired. Valve 'in governor mechanism 239 operates to reduce the fuel flow and hence the speed, and valve lat in mechanism l'i i operates to decrease the pitch and hence the torque, each correction involving a process previously described. Concurrently, there is a tendency for the speed to increase as the torque is reduced by mechanism I14; similarly. there is a tendency for the torque to increase as the speed is reduced by mechanism 240. ..he latter peed and torque effects are temporary, however, the process of correction being continuous until both speed and torque have desired values.

Operating condition (G) TORQUE LOW; ENGINE SPEED HIGH In condition (G), the engine overspeeds and the torque is lower than desired. Again valve operates to reduce the fuel flow and hence the speed. Simultaneously, valve 256 temporarily produces a torque increase and valve l8!) operates to increase the torque and to thereby tend to further decrease the speed. The process continues until both speed and torque are restored to desired values. The relative extent of compensation by valves I89 and 2% depends upon the relative extent of variation of speed and torque from desired values.

Operating condition (H) TORQUE HIGH; ENGINE SPEED LOW In operating condition (H), the engine speed is lower than desired and the torque is higher than the predetermined value. Valve [8D is therefore above its neutral position and valve 250 is below its neutral position. Assuming that the speed is not sufiiciently low to permit opening of port 212, then oil is being drained from conduit it to port 234 and thence thru conduit 232 to drain conduit 8%. The resulting decreased torque tends to increase the speed. Simultaneously, valve 259 is below its neutral position and therefore permits flow from conduit 235 to conduit 232 and the fuel flow and engine speed are increased. The process continues until desired values of both speed and torque are restored.

If the speed falls far enough below the desired value to permit valve 25!? to uncover port 2'12, the process followed in restoration of speed and torque values is a combination of the processes outlined in reference to conditions (A) and (H).

Operating condition (I) TORQUE CORRECT; ENGINE SPEED Low In condition (I), the engine speed is low, while the torque has the desired predetermined value. In this condition, valve I86 is in its neutral position, while valve 259 is below its neutral position. The process of correction involves those previous-- ly explained.

Operating condition (J) TORQUE LOW; ENGINE SPEED LOW In condition (J) both torque and engine speed are below their respective desired predetermined values, and hence both valves we and 25B are below their respective neutral positions. Flow may occur, therefore, from conduit 18 thru port 230, past undercut 228, into conduits 48 and 238. From conduit 236 the flow continues thru port 266, past undercut 250, into conduit 282. Both the pitch control pressure (106) and the motor pressure (m) are thereby increased and the desired values of speed and torque are restored. The process may involve one or more of those previously explained in connection with conditions (A) to (I), depending on the absolute and relative extents to which speed and torque are initially below desired values.

In the intermediate range of movement of control lever 286, in which both the speed and 15 the torque are increased as the lever is advanced, deviations from desired conditions are compensated in a manner similar to one or another combination of processes explained in connection with the conditions (A) to (J), inclusive.

It is thus shown that the fuel flow and hence the engine speed is controlled by the governor mechanism 246. It is also shown that there is a temporary slight variation in torque when valve 250 is temporarily disturbed from its neutral position due to deviation of the engine speed from a predetermined value.

It is also shown that the engine torque is a function of the response of the pressure (176) in conduit 46 to movement of the control lever 286, the lever position determining the value of the pressure (pa) in pressure regulator 12, and the control valve mechanism I I8 determining the value of pressure (pi) corresponding to any given value of the pressure differential (p p It is further shown that when the engine temperature exceeds a predetermined value, the value of the differential MI -P decreases from the value of the compressor pressure differential until the limiting temperature or a desired function of the limiting temperature is restored.

The control valve mechanism H3 has two additional functions, namely; it determines the rate of change of engine torque and hence the engine speed, as the control lever is advanced or retarded, thus being an acceleration and deceleration control of both torque and speed; and, it serves as an altitude control since, as previously explained, the compressor pressure differential decreases as altitude increasse or as the air density decreases.

FIGURE 2 Referring to the drawing, Figure 2, there is shown diagrammatically the internal combus' tion engine of Figure l and connected thereto: a tube 56 for supplying air to the control apparatus at the static pressure (71 in the air entrance l2; a tube 52 for supplying air to the control apparatus at the static pressure downstream from compressor i4; and a conduit 54 for fuel flowing to the manifold 22 in the engine from a variable delivery fuel pump indicated as 56, which is driven by the engine thru gearing 56 and is connected to a source of fuel by a fuel inlet conduit 60.

There is shown an oil supply conduit 62 for the flow of engine lubricating oil, at a pressure (211) to an inlet conduit 64 and thence to a pump 66 having a constant delivery at any given speed. From pump 66 oil flows at a superatmospheric pressure (112) thru a conduit 334. Conduit 364 is connected by a conduit 366 to a by-pass valve mechanism 338 comprising a body 3H), a chamber 3|2, an aperture 3E4 connecting chamber 352 to conduit 3%, and a drain channel 3H3 connecting chamber 352 to a drain conduit 3l8 which in turn is connected to conduit 62. A valve 320 has one end slidable in a guide 322 in body 356 opposite aperture 3| 4, and has its other end in aperture 3E4 and effective to vary the area of flow therethru from conduit 306 to drain channel 316 as a function of the value of the differential between the pressure (102) in conduit 305 and the pressure (101) in chamber 3l2. A spring 324 is in compression between valve 326 and the upper end of chamber 3|2 and tends to force valve 320 toward a seated position in aperture 3E4 in opposition to the pressure differential (pg-p1). Since the value of pressure (1m) may be assumed to be substantially constant and since the rate of spring 324 and the load thereon is substantially constant, it follows that the bypass valve mechanism 336 maintains the pressure (pa) in conduit 304, and hence in conduit 304, at a substantially constant predetermined value.

Conduit 334 is connected thru a restriction 326 to a first pressure regulator generally indicated as 328 which includes: a body 330 and 2. diaphragm assembly 332, which together form a chamber 334, a diaphragm retainer 335, and a valve 336 attached to diaphragm assembly 332, which includes a diaphragm 340. Valve 338 operates in a seat 342 in body 336. Seat 342 is connected to conduit 82 by a conduit 344. A spring 346, in compression between diaphragm assembly 332 and a retainer 348, tends to move valve 338 toward seat 342 with a substantially constant force in opposition to a force produced by the differential between the pressure (pa) in chamber 334 and the atmospheric pressure (p) acting on diaphragm assembly 332. The gage pressure (m) is therefore substantially constant when the position of support 348 is constant and hence when the load on spring 346 is substan tially constant.

The particular value of pressure (733) in chamber 334 is controlled by the position of support 348 which is operable by a cam 350 mounted on a shaft 352 which is rotatable thru an arc of predetermined length by a manually controlled lever 354.

Similarly, conduit 304 is connected thru a restriction 356 to a second pressure regulator generally indicated as 358 which includes: a body 360 and a diaphragm assembly 362, which together form a chamber 364, a diaphragm 3'10, a diaphragm retainer 366, and a valve 368 attached to assembly 362. Valve 368 operates in a seat 372 in body 363. Seat 372 is connected to conduit 62 by conduits 314, 376 and 3I8. A spring 318, in compression between diaphragm assembly 362 and a retainer 363, tends to move valve 368 toward seat 312 with a substantially constant force in opposition to a force produced by the differential between the pressure (278) in chamber 364 and the atmospheric pressure (p) acting on the upper side of diaphragm assembly 362. The gage pressure (298) is therefore substantially constant when the position of support 380 is constant and hence when the load on spring 318 is substantially constant.

The particular value of pressure (298) in chamber 364 is controlled by the position of support 386 which is operable by a cam 382 mounted on a shaft 384 which is rotatable thru an arc of predetermined length in response to movement of a manually controlled lever 546.

Chamber 334 in first pressure regulator 328 is connected by a conduit 388 to a first control valve mechanism 390 including a housing 392 having two adjoining chambers 394 and 396 in its opposite ends. A bellows 398 is fixed to body 392 in the right-hand end of chamber 394 and is connected to a valve 400 which operates in a guide 402 at the right-hand end of chamber 396. The end of valve 400 is contoured and is operable in a seat 40I at the right-hand end of conduit 388 in response to movement of bellows 398, and in opposition to a spring 464, to increase the effective area of seat 40! and hence to increase the flow to chamber 396. Chamber 396 is connected to a conduit 436 and to another conduit 438 which is acreage 'valvellw and flows from chamber 396 thru con- "du'it 408 and restriction 4'!!! to conduit 62. The motor pressure (231) increases as the pressurercps) increases or as the efiectiveereaof: seat :49 i increases and hence as bellowsfi '8 col-lapses Similarly, chamber '3'64 =in second pressure regulator 358 is connected'by a-conducit 4i6 to a-seconcl -control valve mechanism -H8 including a housing 420 having two adjoining-chambers 422 and 424 in its opposite-ends. A bel1ows 426 is fiXed in body 428 =-the -right-hand-end of chamber 422 and is connected to a valve MB which opera'tes in a guide tfillatthe right=hand= end ofchamber 424. Inc end-of va1ve42 8 is contoured and is operable ina seat 429 at the right-hand endof conduit 416 in'response to movementn'of bellows 42B, and in opposition to ia:spring'.432,x;to increase the: eff ective area of seat 42 9 and hence to increase the flow-tdchamber 42 4. .Chamber 42'4 isconnected .to a COI1dl1il3'l434 which is connected to-another conduit 436.

One end 'oficonduit-436 is connected to-the' interiorof a bellows 438- in a pitch control pressure regulator indicated as 440. The other end 0f conduit 436is=connectedthru .a fixed restriction M2todrainconduitsfilfi .andl3'l8. The pressure "(174) zin conduits 1434 and .436 and in bellows 14.38 is a measure of the desiredrtorque and is regulated as a function of the value of pressure (pa) in chamber-364, the contour of valve .428, and the position of valve 428 in relation toxseat;429. Oilenterszchamber 424 in control valve-mechaniszn H8 thru conduit 4.16, vpassesvalve 428, sand flows fromtchamber 424.-thru conduits 434 and 436, then thru restriction 4e42, :whence the snow: continues to drain conduits 31.6 and 3L8. The-pres- :sure' (1%) measuring the.- desiredatorque; increases as-:the;pressure (p8) increases or'as the-effective area of seat 429 increasesandlhence :as bellows .426 collapses.

Controlvalvexmechanism73% and'A l 8.. areeconnected by =a.oonduit 1.444 to equalizethepressures in chambers 39.4 .andz422. Chamber f3941l5 connecteda'by a conduit .446, .thruqa-restriction 443, toz'the compressor discharge. pressuretubexmsand the pressure (11 in conduits 446 and 444 andtin chambers 3.94 and 24.22, tends to collapse bellows 1398 ands-426.

The-interiorof bellows 426 is'connected to-a conduit-450 and bellowsai398-is connected toeon- -duit:450 by anotherconduit 145i. Conduit fl-is connected to '.-the compressor entrance 2 pressure tube 50, whence therespective interiors sofab l- 1OWS398 and 426 -are always subjectato 'thepressure (p 'y which tends to extend theibellows.

-A :thermal control 452 is connected to-cQnduit ;and;also byymea-ns of: a conduit-454m conduit 446 at -a,p oint in;conduit:446 :betweenrestriction 448 and5control valve mechanism 3330. ,Thermal contro1l452 comprisesabo'dy 45,6 havingiaiwall 4.58 sepa a i -a vle ch mbe 1 6. which i eennected to cond i fi irirom-anzo l chambe 462, which is connected to conduitfifl. Qne end of a thin-walled tube- 464115 fixed .t -athei lesed tween valve ilt and seatdll2.

endv ofbody 456 nearest chamber' 462 a-rld hasat tached to its other end,vvhichis closed a rod 466 whichis :slidable 'in a centrally located aperture 468 in theiend of body'i45t to whio'htube 564 is fixed. The free end of rod 466 is tcontoured to form a valve 4 6 which is operablein 1a :seat 412 in Wall 458. Tubet464 and rQdJiEG-aremaderrom materials I having substantially erent 'coeilicients'of thermal expansion-and the unit isinstalled in 'the engine with tube 464 exposed to the temperatureofcombustiomgasesin the tailpipe, as shown diagrammatically :Figure l,-or other desired location. As the temperature increases, the-tube 46:2 expands faster than rod 466,=thereby increasing the effective-area of opening -be- Generally; control -452 is madeso that the valve remains-closed until a limiting value or" temperature is exceeded.

*Whenvalve 4191s closed,-as is normally true, the pressure in chambers 394 and 422 :outside bellows 398-and 425 is the same as the pressure in conduit'446 and tube52, there being no-ilow thru restriction 2448 hence the pressure 123 the pressure (p when valve 41-0 is closed. Since the pressures inside bellcws 398 -and -4264s always the 'pressure (p in the tube 5ll,-then-in normal iope-ration below the limiting temperature; bellows 398 amt-42 tare subjecttd the pressure i differential (p epE) When valve .410 is open, however,--as :is the case when the value of-limiting temperatureis exceeded, flow occurs thl'll tub8'a52, =restrictioni448, a portion of conduit 446, an'd conduit 454,thru inlet chamber 43G, past -valve 41itintochamber 462.:and tothe engine thru conduit ifl. The'pressure in conduitsnifid andhence thelp-ressure in conduit i lt is then less than-that in. tube' 52,- because of the pressure 'drop -across restriction Me', theipressure decrease being a 'function of the respectiveareas'oi restriction AeB- andof the opening past valveil'tii. When-thevalve is. open -therefore, thepressure (-PEXiSlESS than the pressure (p- :andubellows i-ZBB and; 426' are subject to' the pressure 'cdifferential (p eqJ .which,- in th is case,-is less than thedifierential In 11 alve 4M .inscontrol mechanism 390 --is subject to a closing force due to springv1404and an opposite rforce :due tc the differential p p Since theperformance characteristics ofsp'ring 4134 are constant, .itvfollows that for every value of the pressure differential-(p -ap' there-"isa predetermined positionof value 400 in seat -Mil and hen'ee a predetermined area of flow past :the valve, depending on its contour. :For a :cgiven contour, when the ,temperature 'does notcexeeed the predeterminedlimitingvalue at which-"thermal control valve 41 El opens, it 'fol-lowssthat :the motor pressure (p1) in conduits 406 and 414 varies-as a function of the'pressure (p3) and= the pressure differential '(p -p Similarly, valve 42-8 in 6 control mechanism= 4 I8 is subject to aclosing force due -to aspring i432 andan opposite-force due to the difieren tial (PB-411E) Since the performance -"chare3cteris tics-oi spring432 are constant, it "follows that for every value of (the pressure differential (p p there is a corresponding 'pos'itioncf valve428 ,in seat 429, and I hence a'jcorrespOridingiarea. of flow pastthe valve depe'nding on'gits contour. 'For any. given contour, .when therten perature :does not exceed the predetermined limitinevalue a h hxth the ma qoetro sa v 428 iqnenseit fol ows-that ainxs ntlu t a d 4:35, th g essun he) ameesur nsvdesired t qu 19 varies as a function of the pressure (pa) and the pressure differential (p p The motor pressure (217) in conduit M4 is used to control the fuel flow in the following manner. The hydraulic motor 4I2 comprises a body 47-4 having a generally cylindrical bore 476 in which there is a piston 418, a rod 480, and a lever 482 for operating the delivery varying means associated with pump 56. Piston 418, rod 489, and lever 482 are so connected that movement of the piston toward the right causes counterclockwise movement of lever 482 and increases the pump delivery. The piston 418 is subject to a motor pressure differential between the motor pressure (in) in a chamber 484 at the left-hand end of bore 416 which is connected to conduit 4M, and the pressure (211) in a chamber 436 at the righthand end of bore 416, chamber 486 being connected to one end of conduit 62. A spring 480 biases the piston in opposition to the motor pres,- sure (717). Since the pressure (121) and the rate of spring 488 are substantially constant, it follows that the pump delivery varies as a function of the motor pressure (217), increasing as the motor pressure increases.

A measure of the actual torque is obtained by use of a torque meter, shown diagrammatically as 490, which is similar in all respects to the torque meter I90 of Figure 1. The torque meter is connected to the engine shaft and a force measuring the actual shaft torque is transmitted thru a lever 493 by a spring 492 to one end of a piston 494 in a pressure control mechanism 496. The mechanism 496 comprises a body 498 having a cylindrical bore 500 opening at one end of body 498 for admission of piston 494 which is slidable in the bore. The other end of body 498 is closed; and, between the closed end of body 498 and piston 494, there is a wall 592 which forms chambers 504 and 506, respectively, on the upstream and downstream sides of a valve 508 which is attached to piston 494, and which varies the effective area of flow thru a valve seat 5l9 in wall 502, in response to movement of the piston. Chamber 504 is connected to conduit 304 and is therefore subjected to the relatively high pressure (:22).

Chamber 506 is connected to the interior of a bellows 5|2 in the pitch control pressure regulator 440 by a conduit 5M; and also by a conduit 5|6 which is connected thru a restriction 5l3 to drain conduit 3l8. Bellows 5|2 and 438 are identical in the embodiment of Figure 2 but may be of different sizes, if necessary, to satisfy partic- .ular design or functional requirements. In operation, the piston 494 is subject to the force of spring 492 and an opposite force resulting from the pressure in chamber 506 which tends to move valve 508 toward its seat. When the force due to spring 492 exceeds the force due to the pressure in chamber 506, the piston moves upward. to increase the opening of valve 508 and hence to increase the flow of oil from conduit 304, to chamber 504, past valve 508, into chamber 506 and therefrom thru conduit 5I6 and restriction 5l8.

The position of piston 494 at diiferent conditions of equilibrium varies slightly depending on the design of valve 508, and the corresponding variation in movement of lever 493 depends on the rate of spring 492. The pressure in chamber 506 and hence the pressure (:05) in bellows 5i2 is proportional to actual torque according to a substantially constant ratio of the pressure (115) to the torque measured by torque meter 490.

20 The restriction 518 provides continuous flow past valve 508, thereby rendering it possible for the pressure in chamber 505 to decrease when the torque, and hence the force of spring 492. decreases and piston 494 moves downward to close valve 508.

The pitch control pressure regulator 440 includes a. body 520 and a chamber 534 to opposite sides of which bellows 5| 2 and 438 are fixed. The unsupported ends of bellows 5l2 and 438 are connected to each other by a rod 522 with which one end of a lever 524 has a pin and slot connection, the other end of lever 524 being hinged at a bearing 526 which is fixed in body 520. At a point between its ends, lever 524 is connected to the end of a valve 528 which is operable in a seat 530 in response to movement of lever 524 and effective to vary the area of flow past valve 528. Chamber 534 is connected to drain conduits 316 and 3! by a conduit 536, and is therefore subject to the pressure (291). Seat 530 separates chamber 534 from another chamber 532.

Valve 528 is thus subject to a force proportional to the differential between forces due to the pressures (p5) and (:04), respectively, acting in bellows H2 and 438, which pressures are respective measures of the actual torque and the desired torque. A condition of equilibrium applies when the pressure (p4) equals the pressure Chamber 532 is connected by a conduit 542 to a conduit 544 which in turn is connected to a propeller pitch control shown diagrammatically as 546. Pitch control 546 is responsive to the pitch control pressure (pa) in chamber 532, in-

creasing the pitch and hence the torque as pressure (p6) increases. In the condition of equilibrium referred to, in which the actual torque equals the desired torque or in which pressures (pa) and (114) are equal, it follows that the pressure (206) has a value corresponding to a desired value of propeller pitch and torque.

In the apparatus of Figure 2, the motor pressure (:07) is always greater than the corresponding pitch control pressure (126) in conduit 544. Accomplishment of this is largely a function of the relative sizes of the piston 418 in motor 412, and the corresponding pressure responsive means in propeller pitch control 546; the motor pressure increasing in respect to the pitch control pressure as the area of piston 418 decreases in respect to that of the corresponding pressure responsive means in the propeller pitch control. Fluid is supplied to chamber 532 in pitch control pressure regulator 440, from conduit 408, thru conduits 542 and 544 and governor mechanism 556.

When the pitch control pressure regulator 440 is not in equilibrium, as when the actual torque and hence pressure (215) is greater than the desired torque and hence pressure (294), the pressure (226) is obviously greater than desired. When this occurs, however, the force produced by pressure (:05) in bellows H2 is greater than the force produced by pressure (104) in bellows 438 and lever 524 moves valve 528 to the right, increasing the opening past the valve and reducing the value of pressure (p6). This continues until the pitch and hence the torque decrease so that the value of the pressure (215) is restored to the value of pressure (124).

Similarly, when the actual torque and hence pressure (125) is less than the desired torque and hence pressure (124), the pressure (176) is less than desired. In this case, the unbalance of pressures actingin bellows 512mm actresses lever 524 to move to the left, '-thereby'. moving valve 528 in La closingdirection and increasing the pressure (pclin chamloer1532. The torque -therefo're increases until ca condition of 'equilibrium is again restored.

-The governor mechanism 556 rcoinp'rises ca 1 speed-responsive device indicated: as 55 8F mounted a'body 560fand 'driven hyragea1-562 at a zspeed proportional to'xthe engi-ne. speed. '-In body 550, there is a valve guide 554 and a valve 566*operable there-in' in response to sdevicei'558; which isiconneetedto valve 565 at azgroove568 at the lower end-of-the valve. iAspr-ing 5'li) is in compre'ssidn extending" above body 565. As the enginerspeed increases, the speed responsive-device" 558 tends to move valve 556 upward relative-;-to-.guide -564, in opposition to spring fi'lil;and=valve566xis in --equilibrium "and stationary when the opposed forcesdue' to spring 514" and to device 558 :.are "equal. The; position of spring support 5-12 wis variable by means of a cam-5T4'-which\is op'er- -able on ashaft 515 connected-to: shaft 550 and "hence responsive to movement of control lever -54B. The particular value of engine speed,-'=at which valve 556 is in its equilibrium, positiomis determinedby the: load onspring 510 and hence cby the; position of lever 545.

Valve 555-=is.fprovided with an undercut-518 "andfguide -554 is. provided witha port 580 con- --nected to conduit MES-and a port-532 connected toiconduit"544which is connected tothe prospeller pitch control 545. 1 In its equilibrium, posi- Ltion, valve 565 is moved upward so-=-that--.the npperend ofundercut 518 is slightly above the lower edge of .port'530 sothat there is a path for flow from conduit-40fi at. pressure .(pv) thru port 580, a recess'584 formed by :undercut 5'l8'and port-582 to conduit 544. The port 582 is open-to recess584 thruout the rangeof operation of valve 556. When the predetermined value of: speed-is exceeded, valve'566 is disturbed from itsequi- 'librium: position and risesto increasethe effective-area of flow thruport580,-=and henceeto :increase the flow toconduit 544.

-When flow into conduit 544 isincreased as -a result ofoverspeeding and consequent increased -efiective opening past valve 566, the pitch control pressure (pa) in conduit 544 is temporarily increasedso that the propeller pitch is increased to provide. temporarily increased torque. I Corresponding to the increased flow to conduit-544,

there isa reduction of the value of pressure (-107) in conduit 414. Thus, when the predetermined value of speed is exceeded, thedesired- =speed i restored by simultaneous fuel flowdeorease and torqueincrease.

The torque increase referred to .in the=imme-" "-diately preceding paragraph .is detected'bv-the speeding,#therefore, the effect-of torque increase is temporary,- the speed being-finally established in b6110Ws'5l2 in pitch control between asupp'ort' 51 2 and another support 574 "fixed a to the upper 'endof valve 7 566. valve-566 determine'd length i-n I respect to a c fixed quadrant 552. 1 shaft 384 and a link 554 connects lever- 354 a iever sae mounted on shaft 384 so thati nove- 2'2 fatithe'iidesired' value by re'gulation 'of theisptes sure (:07) in conduits 406 and 4M. Corresponding to the: condition of overspeeding explained above, the 'reactionofiithe apparatus to a' con'ditio'n'of speed-decrease below the desired value is as follo'v'vs: Va'1ve 555 mo'ves downward and, depending in upon the amount df :ispeed de'c'rease, 'decrea'ses "the effective area 6i flowifrom conduit '406' to conduit fi i l. 'lihefihiocrea'se'd 'so that the fuel new is increased. Also,

the f'pitc control-pressure (gas) is decreased the propeller -pitch decreasesf: the torque deereases, 'd the' engine=speed increases, th'erefore th becau'se of the fuel flow' increase and' th torque de'crease. Since the change 'of torque di'stu-rbs equilibrium of regulator 440- and -valve 52B, the t'o'rque is subsequently corrected' to the 5 desired 'value; the fuel flowi being the final means' of i'estoring the engine' spced to the desired value.

Eng ine control lever 548 15? fixed to a -i shaft =550 and which is rotatable th'rui an-arc of: prerated Shaft 558 is connected to 350 and 382: and-' -hence there are pr'ed'etermined valu'e's of ith pressures (-ps) and (908) -ior 'eaeh gine and the engine torque are -therefore iesp'ons'ive to movement of thecontrol lev'er 548,

but a gove'r-normechanism 5 556 is provided to overridehermal control wh'entlie -engine-':- speed exceedspredeterminedlimiting or des'ire'd' values.

During a first predetermined range of mevemerit of control lever 5'48,"from 'z'ero-posi tion to approximately degrees --'inthe 'embodiment shown; the lift or earn- 515'- increases corresponding to an increase '-in-' the predetermined limit- 'ing value-of speed froma minimum v'aluei'to an intermediate greater value which ap roximates 10,000 RfPf Mfiin the particular engin shown. 'simultaneously, the lift of earn increases, so that in steady-state operationat "ny pomt -in -the= first range of lever mbvement, the duel fiovv is "such that the engine 1 temperature @issa preselected-amount less than the limitingrvalue.

- 'I'h'e v lift of scam "382 is z'substantialiy i constant athi'uout. the first range of lever movement, and

provides for a minimumzvalue oil-pressure 110.4) and :hence -minimum torque. -Thus,-in l the-first range, torque has a constant minimum valueand the-engine speed is increased to-an intermediate value somewhat-less than the limiting. value.

-During the second predetermined range .Tof movement of control lever-.548, or approximately from'20-degree to 30-degree positions in the "embdaimentshown; the lift or ca'm5fi5 continuesto increase corresponding to an"inc'rease"'in the predetermined limiting speed" from the inter- "mediatevalue previously referred to as approx- 'im'ately10' ,000" R; P. to the "maximum limit "ingwaluewhich approximates 13 ,000R; PPM" in seine engines of the type 'shovvn in Fig' -l. Simultaneously, the lift of cam 355 continues to increase, so that the fuel fiow to the engine cohtinu'es -to increase as the lever -is-advanoed,

the ruerfiowalways being a; preselected amount less than that required to produce limiting-itemperature in steady-state operation. .The lift-.013

cam.38.2-, inthe second range of levermovement, ;increasesslight1yas the lever is advanced and .the pressureipi) measuring thedesired torque, andshence the .actualtorque. increases mimsa minimum to a slightly greater than minimum remains constant, corresponding to a speed which is the maximum allowable or desired limiting speed. The lift of cam 382 increases to a maximum, however, corresponding to an increase in torque to a maximum value. Since the torque is increased as the lever is advanced, it follows that the fuel flow increases as the lever is advanced, in order to increase the engine brakehorsepower, and thereby maintain the predetermined constant maximum speed. The engine temperature rises as the lever is advanced in this range, and in steady-state operation the temperature most nearly approaches the limiting value when the lever is farthest advanced and hence when speed, torque, and brake-horsepower have maximum values.

During acceleration, as occurs during the interval following advance of lever 548 in which the engine gradually assumes a new condition of steady-state operation, the response of con trol valve mechanisms 390 and M8 to increasing compressor pressure differential is controlled by means including the contour of valves 40!) and 428 and the area of restriction 448, so that the engine operates at or near the limiting temperature until the particular setting speed value is closely approached.

A second function of the contour of valves 400 and 428 and of control mechanisms 390 and H8 is to compensate changes in altitude. Increased altitude is accompanied by decreased air density and decreasing values of the compressor pressure differential and thus affords automatic altitude compensation as a function of compressor characteristics. Use of contoured valves such as 400 and 428, however, render it possible to regulate density compensation somewhat independently of the compressor characteristics and to include in design of the respective contours of valves 400 and 428 satisfactory treatment of the problem of acceleration.

It has thus been shown that the fuel and torque control apparatus of Figure 2 regulates the speed and torque of the engine and the fuel flow thereto as functions of the compressor pressure differential and of manual control. It has also been shown that speed and temperature in excess of predetermined values are prevented by an override governor mechanism and a thermal control. The process by which the engine performance is maintained at the desired condition indicated by position of the manual control lever has been shown to be a co-operative function of the governor mechanism 556 and the pitch control pressure regulator 440. Predominant control of acceleration and altitude compensation are shown to be inherent functions of the control valve mechanisms 390 and M8.

While the use of single bellow responsive to an air pressure differential between the static compressor discharge pressure and the static compressor inlet pressure is specified in both Figures 1 and 2, alternate arrangements include equivalent use of single bellows or pairs of bellows responsive to the compressor rise, the absolute compressor discharge pressure, the compressor discharge gage pressure, the absolute compressor inlet impact pressure, the dilferential between the compressor discharge pressure and the compressor inlet impact pressure or to the difierential between static and impact pressure in the course of air flow.

Whil the embodiments of my invention shown and described herein specify use of collapsible bellow as pressure responsive means, the invention does not preclude employment of an equivalent arrangement of pressure responsive pistons, diaphragms, or other means. Similarly, the use of engine oil pressure specified herein does not preclude employment of any suitable hydraulic fluid properly applied.

Other terms and expression which I have emplayed are used as terms of description and not of limitation, and I have no intention in the use of such terms and expressions of excluding any equivalents of the features shown and described or portions thereof, but recognize that various modifications are possible within the scope of the invention claimed.

I claim as my invention:

-1. Fuel control apparatus for an internal combustion engine having a pump for delivering fuel thereto, said pump having means for varying the delivery thereof, comprising: hydraulic motor means responsive to a motor fluid which is separate from said fuel and whose pressure is responsive to an air pressure in said engine for actuating said delivery varying means; valve means responsive to the engine speed and adapted to vary the response of said motor to said fluid pressure so as to increase said pump delivery and hence restore said speed when said speed temporarily falls below a predetermined value, and to maintain said increased pump delivery after restoration of said speed to said value; said valve means being also adapted to vary the response of said motor to said fluid pressure so as to decrease said pump delivery and hence restore said speed when said speed temporarily exceeds said predetermined value, and to maintain said decreased pump delivery after restoration of said speed to said value; and manually operated mean for varying the action of said valve means so that the engine speed has a substantially constant pre- 7 determined value which is a selected function of the operation of said manually operated means.

2. For an internal combustion engine having a compressor for delivering combustion air thereto, a shaft connecting said engine to a variable load mean for varying said load and thereby varying the torque transmitted by said shaft; torque control apparatus comprising: first hydraulic means responsive to an air pressure in the engine and adapted to regulate a first pressure in said first means proportional to the desired value of said torque; second hydraulic means, responsive to said first pressure and to the actual engine torque, for regulating a second pressure in said second means, said load varying means being responsive to said second pressure and adapted to maintain the value of said actual torque equal to the value of said desired torque; governor valve means and a conduit for transmitting said second pressure thereto, said governor valve means being responsive to the engine speed and adapted to increase said second pressure and hence said actual torque when a predetermined value of engine speed is temporarily exceeded; and manually operated means for varying said predetermined value; whereby said shaft torque is a predetermined function of the operation of said first means, said manually operated means and the engine speed.

3. For an internal combustion engine having a pump for delivering fuel thereto, said pump having means for varying the delivery thereof, a

shaft connecting said engine to a variable load, and means for varying said load and thereby varying the torque transmitted by said shaft, fuel and torque control apparatus comprising: first means, responsive to the net value of the desired and actual torque of said shaft, for regulating the operation of said load-varying means as to maintain equalinof the respective values of said actual desired torques; and second means, responsi-ve to the engine speed and coasting with said first means, for modifying the action of said first means to increase the value of said actual torque and simultaneously operating said delivery varying means to decrease said fuel flow, thereby decreasing said engine speed; whereby said shaft torque is a desired function of the operation of said first means, and whereby there is a preselected relationship between said torque and the fuel fiow to the engine a predetermined value of speed.

4. For an internal combustion engine having a pump for delivering fuel thereto, said pump havmg: means for varying-the-delivery thereof, a shaft connecting said engine to a variable" load, and means responsive to a control pressure for varying said load and thereby varying to thetorqu'e' transmitted by said shaft as a direct function of said control pressure;- fuel and torque control apparatus comprising: a source of hydraulic fiuid, motor means for controlling said fuel delivery varying means in response to a variable pressure in saidfluid; governorvalve" means responsive to the speed ofsaidengine: and conduit means; connectedto said" governor valve means; including a" first" conduit connecting said" governor valverneans with said motor'means; and' a second conduit connecting said governor valvemeans' with saidload-varying means; said "governor means being, ad'apted'to cont'rolithe fi'owthru sai'd'oondui't. means so't'ha't, when saidlspeed exceeds a predetermined value, saidccmtrol'lpressure is" varied in a, torque-increasing sense andssaid' variable pressure is varied in a, pump delivery-decreasing sense.

For an internalcombustionengine having a pump. for. delivering iuel.thereto,. said. pump-haw ing meansfor varyingthe delivery thereof}. a shaft. connecting. saidengine to avariable. pitch propeller, means-ion varying, the. propeller. pitch, andrthereby varying the-torque transmitted by, sa d shalt; fuel andtorque. controlrapparatus:

1 a source of hydraulie fluid under e, means .ior, creating a. .moton pressure. in

press.

said fluid, motor means foricontrolling'saidiuel delivery varying means; in response :to-said motor pressure; meansronerativelyassociated with said motor meansfon regulating said motor pressure over. apredetermined; range of; values; conduitv means,- connecting said sourcesv andv said;- pitch varying means for, supplyingfiuid thereto at a control pressure; means connected-to: said 1 com duit mean-safer regulating; said ,oontrollpressure over a: ran of values v substantially-" different from the range of said motor pressures; ta; pasconnecting, saidv motormeans. at an point. thereinsubj est tor said; motor: pressure Withisaiclconr iiitgl'. l he atr apoint:therein-subjectto said control pressure; and governor means connected to said passage ion controllingthe flow thru said passage in response. toczengine.speed-and adapted whenizsaid .speediexceeds predetermined value' to; vary. said: control lpressnre in a torque-increas ing: sense: and tovvary said motor pressure -in pnmpz deliverydecreasing: sense-2 6. For an internal combustion engine having a pump for d'eliverying' fuel thereto, said pump having means for varying the deliverythere'of, a shaft connecting said engine to a variable load, and means responsive to a control pressure for varying said load and thereby varying the torque transmitted by said shaft as a direct function of said control pressure; fuel and torque control apparatus comprising: a source of hydraulic fluid, motor means for controlling said fuel delivery varying means in response to a variable pressure in said fluid, means associates; with said motor means for regulating said variable pressure over a predetermined range of values; a conduit means connecting said source and said load varying means for supplying fluid to the latter at-a control pressure; means for regulating said control pressure over a range of values substantially different from said range of said variable pressure, passage means connecting said motor means at a point therein subject to said motor pressure and said conduit means at a oint therein subject to said control pressure; and governor means for controlling the flow thru' said passage means in response to engine speed and adapted when said speed departs in one sirestion from a predetermined value to vary said control pressure and said variable pressure in op: posite senses, so as to'vary'said torque and said fuel pump delivery in the proper respective directions to restore said speed to" s'a'id. predetermined value.

'7. For an internal combustion engine having a pump for delivering fuel thereto, said pump having means for varying the delivery thereof, a shaft connecting said engine to a variable load, and means for varying saidload and thereby varying the torque transmitted by said shaft; fuel and torque control apparatus comp-rising: first and second sources of hydraulic fluid at relatively low'and high pressures, respectively; a first conduit connected to said first source, a second" conduit connected to said second source, a third conduit connected to said load va'r'yirig means, control means forf regulating. a control pressure'in said third'conduit, said lo'a'd vary'in'g" means being directly responsive to said control pressure; a motor" meansior" controlling said fuel deliveryvarying' means, a fourth conduit con"- nected' to said m'ot'or means, said motor means being responsive to thepr'essure" in said fourth conduit; governor meansresp'ons'ive' to the engine speed: first,.secon'd", third; and four'th son I nections" between" said governor means and said" first, second, third and" fourth conduits, respectively, for the flow of fluid'frbniat' least o'rie of saidconduits to at least one" other of said conduits? said governor means being effective to regulate said motor pressure and; when the engins speed" exceeds a predetermined value, to permit flow'offiuid from said fourth conduit to said first conduit thereby reducing said'motor pressure and hence the fuel now; said governor means being simultaneously" effective when the engine speed temporarily exceeds "said" pre determined value to permit flow of'fluid from said'second' conduit to'sa'id third'conduit thereby temporarily increasing said control pressure and" hence said to'rque; whereby said torque is" .a predetermined furi'ctibn of the operation of said control means-and said peed; and whereby thefuel flow is apre'd'termined function of said speed'and torque. w H v 8; For an internal cbn'rbbstion engine" aving amen-compressor and'aiuelpurrip 'for delivering combustion air and fuel thereto, said pump having means for varying the delivery thereof, a shaft connecting said engine to a variable load, hydraulic means responsive to a control pressure for varying said load and thereby varying the torque transmitted by said shaft as a direct function of said control pressure, and a control lever; fuel and torque control apparatus comprising: first and second regions of hydraulic fluid at relatively low and high pressures, respectively; control means responsive to the compressor discharge pressure in said engine for regulating said control pressure, a third region of fluid at a motor pressure, said fuel delivery varying means being responsive to said motor pressure; first manually operated means and thermal control means responsive to a temperature in the engine for modifying the regulation of said control pressure by said control means; governor means connected to said first, said second, and said third regions and to a source of said control pressure, said governor means being responsive to the engine speed and effective to maintain a predetermined value of engine speed at the value of said torque corresponding to the value of said control pressure, by regulating the flow of fluid between said third region and at least one of said first and second regions and said source of said control pressure; second manually operated means for varying said predetermined value of speed, and a connection between said first and second manually operated means and said control lever; whereby said torque is a function of said compressor discharge pressure, said temperature, and the operation of said control lever; whereby the fuel flow is a function of said speed, said torque, and the operation of said control lever; and whereby said control lever is operable thru predetermined intervals in which the engine torque, the engine speed, or

both said torque and said speed are varied in response to movement of said control lever.

9. For an internal combustion engine having an incorporated air compressor and a fuel pump operated by said engine for delivering combustion air and fuel, respectively, thereto, said pump having means for varying the delivery thereof; fuel control apparatus comprising: a conduit for the flow of compressed air from said engine, first means responsive to the pressure in a portion of said conduit for controlling said fuel delivery varying means, and second means for modifying said pressure when a predetermined value of temperature is exceeded; whereby the fuel flow is a function of said air pressure and the operation of said second means.

10. For an internal combustion engine having a compressor for delivering combustion air thereto, a shaft connecting said engine to a variable load, and means for varying said load and thereby varying the torque transmitted by said shaft; torque control apparatus comprising: a conduit for the flow of compressed air from said engine, first means responsive to the pressure in a portion of said conduit for controlling said loadvarying means, and second means modifying said pressure when a predetermined value of temperature is exceeded, whereby the engine torque is a function of said air pressure and the operation of said second means.

11. For an internal combustion engine having a pump for delivering fuel thereto, said pump having means for varying the delivery thereof, a shaft connecting said engine to a variable load, and means for varying said load and thereby 28 varying the torque transmitted by said shaft; fuel and torque control apparatus comprising: a conduit for the flow of air from said engine, valve means responsive to the engine speed; first means, responsive to the pressure in a portion of said conduit for controlling said fuel delivery varying means; second means, responsive to said pressure and to said valve means, for controlling said load-varying means; and third means for modifying said pressure when a predetermined value of temperature is exceeded; whereby the fuel flow and the engine torque are functions of said pressure and/or said speed, and said pressure being subject to modification as a func- 7 tion of the engine temperature.

" torque control means so that the engine will operate at predetermined related values of speed and torque, under varying operating conditions.

13. For an internal combustion engine having means for delivering compressed air and fuel thereto, a fuel and torque control apparatus comprising: means for controlling the fuel flow to said engine, means for controlling the output torque of said engine, and means, responsive to engine speed and to an air pressure in said engine which varies proportionally to the rate of mass air flow through said engine, for coordinately regulating both the fuel flow control means and the output torque control means so that the engine will operate at a selected substantially constant speed and varying torque, under varying operating conditions.

14. For an internal combustion engine having means for delivering compressed air and fuel thereto, a fuel and torque control apparatus comprising: means for controlling the fuel flow to said engine, means for controlling the output torque of said engine, and means, responsive to engine speed and to an air pressure in said engine which varies proportionally to the rate of mass air flow through said engine, for coordinately regulating both the fuel flow control means and the output torque control means so that the engine will operate at a selected substantially constant torque and varying speed, under varying operating conditions.

15. For an internal combustion engine having means for delivering compressed air and fuel thereto, a fuel and torque control apparatus comprising: means for controlling the fuel flow to said engine, means for controlling the output torque of said engine, and means, responsive to engine speed and to an air pressure in said engine which varies proportionally to the rate of mass air flow through said engine, for coordinately regulating both the fuel flow control means and the output torque control means so that the engine will operate at desired related values of speed and torque, under varying operating conditions.

16. For an internal combustion engine having means for delivering compressed air and fuel thereto, a fuel and torque control apparatus comprising: means for controlling the fuel flow to said engine, means for controlling the output torque of said engine, and means, responsive to engine speed and to an air pressure in said engine which varies proportionally to the rate of mass air flow through said engine, for coordinately regulating both the fuel flow control means and the output torque control means so that the engine will operate at a selected substan tially constant speed and varying torque, under varying operating conditions, throughout an engine operating range between minimum permissible engine speed and a predetermined intermediate speed.

17. For an internal combustion engine having means for delivering compressed air and fuel thereto, a fuel and torque control apparatus comprising: means for controlling the fuel flow to said engine, means for controlling the output torque of said engine, and means, responsive to engine speed and to an air pressure in said engine which varies proportionally to the rate of mass air flow through said engine, for coordinately regulating both the fuel flow control means and the output torque control means so that the engine will operate at a selected substantially constant torque and varying speed, under varying operating conditions, throughout an engine operating range between a torque slightly greater than the permissible minimum and a maximum torque corresponding to maximum brake-horsepower of the engine.

18. For an internal combustion engine having means for delivering compressed air and fuel thereto, a fuel and torque control apparatus comprising: means for controlling the fuel flow to said engine, means for controlling the output torque of said engine, and means, responsive to engine speed and-to an air pressure in said engine which varies proportionally to the rate of mass air flow through said engine, for coordinately regulating both the fuel flow control means and the output torque control means so that the engine will operate at desired related values of speed and torque, under varying operating conditions, throughout a predetermined intermediate engine operating range.

19. For an internal combustion engine having a pump for delivering fuel thereto, a said pump including means for varying its delivery, a fuel and torque control apparatus comprising: an hydraulic motor for regulating the fuel delivery means of said pump; an hydraulic pressure regulator, responsive to an air pressure in said engine which varies as a selected function of the rate of mass air flow through said engine, for controlling the torque of said engine; and a governor mechanism, responsive to engine speed, connected to and adapted to so act upon said pump delivery means and regulator that the engine will operate at desired related values of speed and torque, under varying operating conditions.

20. A fuel and torque control apparatus according to claim 19, wherein said governor mechanism is also responsive to a manual control lever, whereby the torque and/or speed of the engine corresponds to the position of said lever.

21. A fuel and torque control apparatus according to claim 19, including a thermal control pressure regulator is responsive to an air pressure in said engine which varies proportionally with the rate of mass air flow through said engine, whereby the fuel supply to said engine varies proportionally with the air supply thereto.

22. A fuel and torque control apparatus according to claim 19, wherein said torque control pressure regulator is responsive to an air pressure in said engine which varies proportionally with the density of the atmosphere outside said engine, whereby the operation of said control apparatus is compensated for variations in atmospheric density.

23. A fuel and torque control apparatus according to claim19 including, a thermal control device operatively connected to said torque control pressure regulator and responsive to the temperature of the combustion gases in said engine, for modifying the action of said regulator so that the speed of the engine is so regulated that the temperature of the engine never exceeds amaximum permissible value.

24. For an internal combustion engine, connected by a shaft to a variable pitch propeller having means for varying its pitch, said engine having a fuel pump with means for varying its delivery to said engine; combined fuel and torque control apparatus comprising: first means, responsive to the diiference between the actual torque and a desired torque of said shaft, and operatively connected to said pitch varying means and to said fuel delivery varying means, said first means being adapted to vary the operation of said fuel delivery varying means, and regulate the operation of said pitch-varying means so as to maintain equality between said actual and desired torques; second means, responsive to engine speed and operatively connected to said first means, for modifying the action of said first means so as to simultaneously increase said actual torque and decrease said fuel delivery, thereby decreasing said engine speed, when said speed exceeds a predetermined value, and conversely increasing said engine speed when it falls below said value, whereby said actual shaft torque is a desired function of the operation of said first means and said engine speed is substantially constant.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,187,120 Gosslau et a1. Jan. 16, 1940 2,303,998 Holley Dec. 1, 1942 2,322,303 Martin June 22, 1943 2,391,323 Martin Dec. 18, 1945 2,403,371 Ifield et a1 July 2, 1946 2,405,888 Holley Aug. 13, 1946 2,414,322 Mock Jan. 14, 1947 2,424,035 Ifield July 15, 1947 2,429,005 Watson et a1 Oct. 14, 1947 2,447,267 Mock Aug. 17, 1948 2,450,535 Watson et a1 Oct. 5, 1948 2,457,595 Orr Dec. 28, 1948 2,525,460 Roesch Oct. 10, 1950 

